Fabrication of GeO2 microspheres /hierarchical porous N-doped carbon with superior cyclic stability for Li-ion batteries

Carbon confined GeO2 hollow spheres for stable rechargeable Na ion batteries†

Germanium (Ge) based nanomaterials are regarded as promising high-capacity anode materials for Na ion batteries, but suffer fast capacity fading problems caused by the alloying/de-alloying reactions of Na–Ge. Herein, we report a new method for preparing highly dispersed GeO₂ by using molecular-level ionic liquids (ILs) as carbon sources. In the obtained GeO₂@C composite material, GeO₂ exhibits hollow spherical morphology and is uniformly distributed in the carbon matrix. The as-prepared GeO₂@C exhibits improved Na ion storage performances including high reversible capacity (577 mA h g⁻¹ at 0.1C), rate property (270 mA h g⁻¹ at 3C), and high capacity retention (82.3% after 500 cycles). The improved electrochemical performance could be attributed to the unique nanostructure of GeO₂@C, the synergistic effect between GeO₂ hollow spheres and the carbon matrix ensures the anode material effectively alleviates the volume expansion and the particle agglomeration problems.

We report a new method for preparing dispersed GeO₂ by using molecular-level ionic liquids as carbon sources. In the obtained GeO₂@C composite material, GeO₂ exhibits hollow spherical morphology and is uniformly distributed in the carbon matrix.

A Low-Cost and High-Capacity SiO x /C@graphite Hybrid as an Advanced Anode for High-Power Lithium-Ion Batteries

Silicon suboxide (SiO _x ) is one of the most promising anodes for the next-generation high-power lithium-ion batteries because of its higher lithium storage capacity than current commercial graphite, relatively smaller volume variations than pure silicon, and appropriate working potential. However, the high cost, poor cycling stability, and rate capability hampered its industrial applications due to its complex production process, volume changes during Li⁺ insertion/extraction, and low conductivity. Herein, a low-cost and high-capacity SiO _x /C@graphite (SCG) hybrid was designed and synthesized by a facile one-pot carbonization/hydrogen reduction process of the rice husk and graphite. As an advanced anode for lithium-ion batteries, the SiO _x /C@graphite hybrid delivers a high reversible capacity with significantly enhanced cycling stability (842 mAh g^-1 after 300 cycles at 0.5 A g^-1) and rate capability (562 mAh g^-1 after 300 cycles at 1 A g^-1). The great improvement in performances could be attributed to the positive synergistic effect of SiO _x nanoparticles as lithium storage active materials, the in situ-formed carbon matrix network derived from biomass functioning as an efficient three-dimensional conductive network and spacer to improve the rate capability and buffer the volume changes, and graphite as a conductor to further improve the rate capabilities and cycling stability by increasing the conductivity. The low-cost and high-capacity SCG derived from rice husk synthesized by a facile, scalable synthetic method turns out to be a promising anode for the next-generation high-power lithium-ion batteries.

Renal Clearable Gold Nanoparticle-Functionalized Silk Film for in vivo Fluorescent Temperature Mapping

Implantable optical sensing devices that can continuously monitor physiological temperature changes hold great potential toward applications in healthcare and medical field. Here, we present a conceptual foundation for the design of biocompatible temperature sensing device by integrating renal clearable luminescent gold nanoparticles (AuNPs) with silk film (AuNPs-SF). We found that the AuNPs display strong temperature dependence in both near-IR fluorescence intensity and lifetime over a large temperature range (10-60°C), with a fluorescence intensity sensitivity of 1.72%/°C and lifetime sensitivity of 0.09 μs/°C. When integrated, the AuNPs with biocompatible silk film are implanted in the dorsal region of mice. The fluorescence imaging of the AuNPs-SF in the body shows a linear relationship between the average fluorescence intensity and temperature. More importantly, <3.68% ID gold are left in the body, and no adverse effect is observed for 8 weeks. This AuNPs-SF can be potentially used as a flexible, biocompatible, and implantable sensing device for in vivo temperature mapping.

Dual-Templating Approaches to Soybeans Milk-Derived Hierarchically Porous Heteroatom-Doped Carbon Materials for Lithium-Ion Batteries

Biomass derived carbon materials are widely available, cheap and abundant resources. The application of these materials as electrodes for rechargeable batteries shows great promise. To further explore their applications in energy storage fields, the structural design of these materials has been investigated. Hierarchical porous heteroatom-doped carbon materials (HPHCs) with open three-dimensional (3D) nanostructure have been considered as highly efficient energy storage materials. In this work, biomass soybean milk is chosen as the precursor to construct N, O co-doped interconnected 3D porous carbon framework via two approaches by using soluble salts (NaCl/Na2CO3 and ZnCl2/Mg5(OH)2(CO3)4, respectively) as hard templates. The electrochemical results reveal that these structures were able to provide a stable cycling performance (710 mAh ⋅ g-1 at 0.1 A ⋅ g-1 after 300 cycles for HPHC-a, and 610 mAh ⋅ g-1 at 0.1 A ⋅ g-1 after 200 cycles for HPHC-b) in Li-ion battery and Na-ion storage (210 mAh ⋅ g-1 at 0.1 A ⋅ g-1 after 900 cycles for HPHC-a) as anodes materials, respectively. Further comparative studies showed that these improvements in HPHC-a performance were mainly due to the honeycomb-like structure containing graphene-like nanosheets and high nitrogen content in the porous structures. This work provides new approaches for the preparation of hierarchically structured heteroatom-doped carbon materials by pyrolysis of other biomass precursors and promotes the applications of carbon materials in energy storage fields.

Fire-safe unsaturated polyester resin nanocomposites based on MAX and MXene: a comparative investigation of their properties and mechanism of fire retardancy

Recently, MXene, as a novel graphene-like nanomaterial, has been found to bestow good flame-retardant and smoke-suppression properties to polymers mainly due to the physical barrier effect of its 2D nanosheets. However, a comprehensive investigation of its chemical components as an important factor for these properties has not been conducted to date. To address this issue, herein, MXene (Ti₃C₂T_x) and MAX (Ti₃AlC₂) were introduced into unsaturated polyester resin (UPR) at same amounts (2.0 wt%). Their structures are different (multilayer for MXene and bulk for MAX), but the chemical components are similar; therefore, it is important to study the influence of the chemical components of MXene on the fire-safety properties of polymers. In this study, 2 wt% MAX was added to the UPR, and the peak heat release rate (PHRR), the total smoke production (TSP), and carbon monoxide production (COP) of the resulting material were reduced by 11.04%, 19.08%, and 15.79%, respectively; these findings demonstrate the important role of the chemical components of MAX: Ti exerts a catalytic attenuation effect on the UPR nanocomposites during combustion. Moreover, a better fire-safety property of the MXene/UPR nanocomposites (reduction of PHRR by 29.56%, TSP by 25.26%, and COP by 31.58%) than that of the MAX/UPR nanocomposites was achieved, which was due to the physical barrier effect of the MXene nanosheets. This study verifies that in addition to the physical barrier effect, the chemical components play a very important role in the fire safety enhancement of MXene-based nanocomposites.

Structure, magnetic anisotropy and relaxation behavior of seven-coordinate Co(ii) single-ion magnets perturbed by counter-anions

A series of mononuclear seven-coordinate complexes with the same coordination unit [Co(BPA-TPA)]²⁺ (BPA-TPA = pentapyidyldiamine) display the different slow magnetic relaxation processes perturbed by the variation of the counter anions.